The Mass Spectra of Giant Molecular Clouds in the Local Group

By Erik Rosolowsky. 2005

164 citations recorded by the source corpus.

We reanalyze the catalogs of molecular clouds in the Local Group to determine the parameters of their mass distributions in a uniform manner. The analysis uses the error‐in‐variables method of parameter estimation, which accounts not only for the variance of the sample when drawn from a parent distribution, but also for errors in the mass measurements. Testing the method shows that it recovers the underlying properties of cumulative mass distribution without bias while accurately reflecting uncertainties in the parameters. Clouds in the inner disk of the Milky Way follow a truncated power‐law distribution with index γ = -1.5 ± 0.1 and maximum mass of 106.5 M⊙. The distributions of cloud mass for the outer Milky Way and M33 show significantly steeper indices (γOMW = -2.1 ± 0.2 and γM33 = -2.9 ± 0.4, respectively), with no evidence of a cutoff. The mass distribution of clouds in the Large Magellanic Cloud has a marginally steeper distribution than the inner disk of the Milky Way (γ = -1.7 ± 0.2) and also shows evidence of a truncation, with a maximum mass of 106.5 M⊙. The mass distributions of molecular clouds vary dramatically across the Local Group, even after accounting for the systematic errors that arise in comparing heterogeneous data and catalogs. These differences should be accounted for in studies that aim to reproduce the molecular cloud mass distributions, or in studies that use the mass spectrum as a parameter in a model.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/7879b83e05e784b76488ae3bee58a92886819cfd

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Citations in the corpus

A general model for the CO–H2 conversion factor in galaxies with applications to the star formation law (2011, background): “…surface density, comparable to the surface density of most molecular clouds in the Local Group (e.g. Solomon et al. 1987; Rosolowsky et al. 2003; Rosolowsky 2005, 2007; Blitz & Rosolowsky 2006; Blitz et al. 2007; Bolatto et al. 2008), is imposed to prevent clouds from having artificially low…”
Theory of Star Formation (2007, result): “An independent analysis by Rosolowsky (2005) finds a similar slope (α = 0.5 ± 0.1), but a somewhat smaller maximum mass (Mu = 3 × 106 M⊙, although this does not include the several most massive clouds).”
THE MAGELLANIC MOPRA ASSESSMENT (MAGMA). I. THE MOLECULAR CLOUD POPULATION OF THE LARGE MAGELLANIC CLOUD (2011, methodology): “In this expression, discussed in more detail by McKee & Williams (1997) and Rosolowsky (2005), N0 is the number of clouds more massive than 21/(β+1)M0, where the distribution begins to turn over (for a meaningful truncation to exist one expectsN0 ≫ 1).”
Quasar feedback: more bang for your buck (2009, methodology): “The clouds are initially placed on the observed size–mass relation (equation 3; determining an initial radius R0 for each cloud of mass Mc), and are distributed in mass according to the observed mass spectrum dN/dMc ∝ M−1.8c (up to a maximum Mc = 107 M ; see Rosolowsky 2005, and references therein).”
Feedback-regulated star formation in molecular clouds and galactic discs (2013, background): “…correlates strongly with molecular gas but not atomic gas (e.g., Wong & Blitz 2002; Schruba et al. 2011) and the mass spectrum of molecular clouds in nearby galaxies is sufficiently shallow that the mass is concentrated in the most massive objects (e.g., Williams & McKee 1997; Rosolowsky 2005).”
The Formation and Destruction of Molecular Clouds and Galactic Star Formation (2015, background): “This tendency is actually observed in Milky Way outer disk, LMC, M33, and M51 (Rosolowsky 2005; Wong et al. 2011; Gratier et al. 2012; Hughes et al. 2010; Colombo et al. 2014) .”
PHYSICAL PROPERTIES OF MOLECULAR CLOUDS FOR THE ENTIRE MILKY WAY DISK (2016, result): “These statistical properties are similar to what has been estimated with smaller samples and over a much smaller range of scales than we use here (Solomon et al. 1987; Williams & McKee 1997; Heithausen et al. 1998; Kramer et al. 1998; Heyer et al. 2001; Rosolowsky 2005; Roman-Duval et al. 2010).”
THE PdBI ARCSECOND WHIRLPOOL SURVEY (PAWS): ENVIRONMENTAL DEPENDENCE OF GIANT MOLECULAR CLOUD PROPERTIES IN M51 (2014, background): “…power-law observed for other extragalactic GMC populations, which tend to be from low-mass dwarf galaxies (e.g., the LMC and M33, Wong et al. 2011; Gratier et al. 2012) or regions of galactic disks without strong spiral structure (e.g., the outer Milky Way and an outer arm of M31, Rosolowsky 2005).”
Star Formation in the Milky Way and Nearby Galaxies (2012, background): “Evidence for a higher value of αcloud has been found for the LMC (Fukui et al. 2001; Wong et al. 2011) and M33 (Engargiola et al. 2003; Rosolowsky 2005).”
STELLAR FEEDBACK IN MOLECULAR CLOUDS AND ITS INFLUENCE ON THE MASS FUNCTION OF YOUNG STAR CLUSTERS (2009, background): “(3b) We now evaluate Equations (3a) and (3b) with βo = −1.7, the observed exponent of the mass function of molecular clouds (Rosolowsky 2005; Reid &Wilson 2006; Muñoz et al. 2007; Wong et al. 2008; Fukui et al. 2008).”
Molecular Clouds in the Milky Way (2015, methodology): “Rosolowsky (2005) followed this study with additional 12CO data from the catalogs of outer Galaxy clouds compiled by Heyer et al. (2001) and Brunt et al. (2003) as well as resolved molecular complexes in Local Group galaxies.”
A physical model for z∼ 2 dust-obscured galaxies (2009, methodology): “For galaxy-scale simulations, we implement a subgrid procedure for including a mass spectrum of giant molecular clouds as singular isothermal spheres, which follow the Galactic mass spectrum (Rosolowsky 2005) and mass–radius relationship (e.g. Solomon et al. 1987).”
The structure of the interstellar medium of star‐forming galaxies (2011, methodology): “For the MW and dwarf/SMC models, we compare with the observed MW and LMC mass functions, respectively (Williams & McKee 1997; Rosolowsky 2005, orange diamonds).”
A UNIVERSAL, LOCAL STAR FORMATION LAW IN GALACTIC CLOUDS, NEARBY GALAXIES, HIGH-REDSHIFT DISKS, AND STARBURSTS (2011, unknown): “The characteristic GMC mass is roughly the two-dimensional Jeans mass in the galactic disk (Kim & Ostriker 2002; McKee & Ostriker 2007), MGMC = σ4 G2Σgal , (3) where σ is the gas velocity dispersion and Σgal is the average surface density in the region of the galaxy where the GMCs form.”